Dual clutch assembly with neutral function and transmission assembly

ABSTRACT

A dual clutch assembly comprises a rotatable second input shaft that surrounds and is concentric with a rotatable first input shaft. A rotatable hub surrounds the first input shaft. A first and a second clutch rotor are connected to the rotatable hub. The first clutch rotor comprises a pulley coupling and a clutch surface. The second clutch rotor comprises a clutch surface. A stationary electromagnetic assembly is mounted between the first clutch rotor and the second clutch rotor. A first armature assembly is coupled to the first input shaft and is configured to couple to the first clutch surface of the first clutch rotor in response to a first electromagnetic signal. A second armature assembly is coupled to the second input shaft and is configured to couple to the clutch surface of the second clutch rotor in response to a second electromagnetic signal.

FIELD

This application provides a two-speed electromagnetic clutch with aneutral function and gear parings for transmitting torque.

BACKGROUND

Superchargers such as Roots blowers or twin screw devices can be lossybecause the engine crankshaft is always connected by a pulley to theinput shaft of the supercharger. Even when the supercharger is idle, thepulley set-up draws torque from the engine crankshaft. Additional lossesoccur when the supercharger lobes continue rotating when boosting is notrequired, and the boosted air must be bypassed around the engine.

Further, it is desirable to have different drive speeds of thesupercharger, but the complexity and footprint required to do so isprohibitive.

SUMMARY

The methods and devices disclosed herein overcome the abovedisadvantages and improves the art by way of a two speed, dual-clutchassembly, which comprises a rotatable first input shaft comprising afirst portion and a second portion. A rotatable second input shaftsurrounds the first portion of the first input shaft, and the secondinput shaft is concentric with the first input shaft. A rotatable hubsurrounds the second portion of the first input shaft. A first clutchrotor is connected to the rotatable hub, and the first clutch rotorcomprises a pulley coupling and a clutch surface. A second clutch rotoris connected to the rotatable hub, and the second clutch rotor comprisesa clutch surface. A stationary electromagnetic assembly is mountedbetween the first clutch rotor and the second clutch rotor. Theelectromagnetic assembly is configured to emit at least a firstelectromagnetic signal and a second electromagnetic signal. A firstarmature assembly is coupled to the first input shaft. The firstarmature assembly is configured to couple to the first clutch surface ofthe first clutch rotor when the electromagnetic assembly emits the firstelectromagnetic signal. A second armature assembly is coupled to thesecond input shaft. The second armature assembly is configured to coupleto the clutch surface of the second clutch rotor when theelectromagnetic assembly emits the second electromagnetic signal.

A gear set, or transmission assembly, can be joined to the dual-clutchassembly to form a two speed, dual-clutch transmission. The gear set cancomprise a rotatable first input shaft and a first gear comprising afirst gear ratio coupled to the first input shaft. A rotatable secondinput shaft can surround a portion of the first input shaft. The secondinput shaft can be concentric with the first input shaft. A second gearcan comprise a second gear ratio coupled to the second input shaft. Acounter shaft can be parallel to the first input shaft. A first outputgear can be connected to the counter shaft, the first output gearcoupled to transfer torque from the first gear. A second output gear canbe connected to the counter shaft, the second output gear coupled totransfer torque from the second gear. The first gear is in constant meshwith the first output gear. The second output gear is in constant meshwith the second gear.

A supercharger assembly can comprise the above dual-clutch transmission.The supercharger assembly can comprise a supercharger input shaftmechanically coupled to the clutch transmission. The superchargerassembly can be configured to selectively convert between a neutraloperation mode, a first drive ratio operation mode, and a second driveratio operation mode in response to the presence or absence of a firstelectromagnetic signal and a second electromagnetic signal. Thesupercharger can comprise a pair of lobed rotors, wherein the pair oflobed rotors are mechanically coupled to the supercharger input shaft,and wherein the neutral operation mode does not transfer torque from theclutch transmission to the pair of lobed rotors.

Additional objects and advantages will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the disclosure. Theobjects and advantages will also be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a dual-clutch transmission.

FIG. 2 is perspective view of a dual-clutch assembly.

FIG. 3 is an exploded view of a dual-clutch assembly.

FIG. 4 is a cross-section view of an alternative dual-clutch assembly.

FIGS. 5A-5C are cross-section views of a dual-clutch transmission withtorque flow paths overlaid.

FIG. 6 is a view of a first input shaft.

FIG. 7 is a view of a counter shaft.

FIG. 8 is a perspective view of an electromagnetic assembly.

FIG. 9 is a view of a first armature assembly.

FIG. 10 is a view of a second armature assembly.

FIG. 11 is a view of a supercharger assembly comprising a dual-clutchtransmission.

DETAILED DESCRIPTION

Reference will now be made in detail to the examples which areillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts. Directional references such as “left” and “right”are for ease of reference to the figures.

The disclosure provides a supercharger assembly 2000, shown in FIG. 11,comprising a two speed clutch, wherein the clutch comprises a neutralfunctionality. Including a neutral functionality limits torque losses.The rotor lobes 2041 can be decoupled from the dual-clutch assembly 101,which permits the lobes to idle. This reduces or eliminates the need forbypassing boosted air. The engine crankshaft remains connected fortorque output via a pulley across the pulley coupling 1103 of thedual-clutch transmission. The first and second clutch rotors 1101 & 900are spun-up with the pulley coupling 1103, which reduces time to torque.A supercharger assembly 2000 can comprise the dual-clutch transmissionfor controlling the flow rate of the positive displacement pump. Thesupercharger assembly 2000 can comprise a supercharger input shaft 2030mechanically coupled to the dual-clutch transmission. For example, acoupler 2010 on the counter shaft 700 of dual-clutch transmission cancomprise a coupling mechanism such as pins 2011 for coupling the countershaft 700 to a supercharger assembly. In a direct-drive set-up, atransfer gear 2020 on the supercharger input shaft 2030 can couple tothe pins 2011 on the coupler 2010. The transfer gear 2020 can transfertorque to a receiving gear 2021 directly. Other mechanisms in a transfercase can be substituted. Rotor lobes 2041 are mounted to rotate as thefirst rotor shaft, which is integrated to form the supercharger inputshaft 2030 in this example, and the second rotor shaft 2031 rotate.Bearings can be included in the supercharger assembly housing 2001. Thesupercharger assembly 2000 can be configured to selectively convertbetween a neutral operation mode, a first drive ratio operation mode,and a second drive ratio operation mode in response to the presence orabsence of a first electromagnetic signal and a second electromagneticsignal in the dual-drive clutch transmission. The supercharger cancomprise the pair of rotor lobes 2041, wherein the pair of lobed rotorsare mechanically coupled to the supercharger input shaft 2030, andwherein the neutral operation mode does not transfer torque from thedual-clutch transmission to the pair of rotor lobes 2041.

The dual-clutch transmission can be used with other superchargers andother driven devices. Two speeds can be selected for transferring torquevia the two clutches in the dual-clutch transmission. For example, whenthe electromagnetic assembly 8000 emits a first electromagnetic signal,as by applying an electric signal to first coil winding 811, the firstarmature plate 1221 is made of a material that is attracted in thedirection of the first coil winding 811, and first armature assembly1200 couples the rotatable first input shaft 600 to the first clutchrotor 1101. The first input shaft 600 can be configured to under-run apulley speed of a pulley connected to the pulley coupling 1103. Choosingthe relative diameters of the first gear 7080 and first output gear 708further impacts the drive ratio of the dual-clutch transmission. By wayof example, the first clutch of the dual-clutch transmission can beconfigured for a “low” setting. Then, the second clutch can beconfigured for a “high” setting, by appropriately selecting the relativediameters of the second gear 7030 and second output gear 703. And, whenthe electromagnetic assembly 8000 emits a second electromagnetic signal,as by applying a second electric signal to second coil winding 812, thesecond armature plate 1011 is made of a material that is attracted inthe direction of the second coil winding 812, and second armatureassembly 1000 couples the rotatable second input shaft 650 to the secondclutch rotor 900, and the second input shaft 650 is configured toover-run the pulley speed of the pulley connected to the pulley coupling1103.

The dual-clutch transmission comprises concentric input shafts in theform of first input shaft 600 and second input shaft 650. The concentricinput shafts can be configured for direct drive of a related device.Constant mesh gears, such as first gear 7080, second gear 7030, firstoutput gear 708, and second output gear 703, can be mounted to the firstinput shaft 600 and to the second input shaft 650. Constant mesh heremeans that the gears are never out of mesh. The gears are not moved orde-coupled from one another to change gears. The constant mesh gearstransmit torque, but are not shifted to do so. The constant mesh gearscan be coupled to a common output shaft, such as counter shaft 700.Counter shaft 700, in the examples herein, rotates whenever one of thefirst or second clutch assemblies 1100, 9000 is engaged (FIGS. 5B & 5C),but counter shaft 700 does not rotate when the dual clutches are in aneutral status (FIG. 5A). The dual-clutch transmission 100 is configuredto provide direct and independent actuation of the gear sets in thetransmission assembly 105. First gear set (comprising first gear 7080and first output gear 708) can be actuated independently from secondgear set (comprising second gear 7030 and second output gear 703).

A two speed, dual-clutch transmission 100 comprises a dual clutchassembly 101 and a transmission assembly 105. Turning to FIG. 1, a firstdual clutch assembly is shown comprising a first cap or dust cover 1240covering a first armature assembly 1200. Dust cover 1241 can be stampedto comprise a shape or can be more uniformly molded, as dust cover 1240(FIG. 2).

Pulley coupling 1103 of first clutch rotor 1101 can receive a pulley,such as a belt, to transfer torque from the crankshaft of an engine oranother torque source such as a motor. Pulley coupling 1103 isexemplary, and other couplings than the illustrated tracks can be used,for example, chain drive, rollers, cones, or other couplings can besubstituted. Electromagnetic mounting hub 800 can comprise a mountingrim 830 for coupling to housing 10. Or, an intervening mounting bracket840 can be included (FIG. 5A). The mounting bracket 840 or mounting rim830 can further comprise features for mounting such accessories asthermal sensors, control electronics, positioning mechanisms, etc.

One aspect of the dual-clutch transmission design permits the joining ofa dry clutch with a wet transmission. And, the driven device can beeither wet or dry. In the example herein, the driven device moves afluid such as air to constitute a dry device. So, housing 10 cancomprise a clutch housing portion forming a dry compartment 11. At leastsome portion of the second clutch assembly 9000 is housed. For example,second armature assembly 1000 can be housed in the dry compartment 11and thereby provided with a dry environment.

A gear housing portion of the housing 10 can then provide a wetcompartment 12 for the transmission assembly 105. The wet compartment 12can surround a portion of the second input shaft 650 and provide afluid-tight container for the portion of the second input shaft 650. Aseal 13 can adjoin the gear housing portion of the housing and thesecond input shaft 650. The seal can be, for example, a hydrodynamic lipseal comprising spiral grooves for pumping lubrication back to the wetcompartment 12. The gears within the wet compartment 12 can fling oil orother lubricating substance around the wet compartment 12, and the seal13 can be designed to return the lubricating substance to the gears. Asimilar seal 15 can be included between first input shaft 600 and secondinput shaft 650 to likewise return lubricating substance. In thisinstance, a bearing 130 can be re-lubricated. Other seals thanhydrodynamic lip seals can be used for seals 13, 15.

FIG. 2 shows the dual-clutch assembly 101 separate from the housing 10and transmission assembly 105. Dust cover 1241 covers first armatureassembly 1200, but shown are portions of first clutch rotor 1101,electromagnetic mounting hub 800, control plug 810, second clutch rotor900, second armature plate 1011 of second armature assembly 1000, andgear surface 651 of second input shaft 650.

The armature assemblies can differ from one another in several respects.In FIG. 3, the coupling surfaces 1012, 1222 of the armature assemblies1000, 1200 are oriented inwardly, towards respective coupling surfaces922, 1105 of the clutch rotors. The first armature assembly 1200 isconfigured as a terminal end of the dual-clutch assembly 101, so thespindle 1210 for torque transfer is designed to couple into thedual-clutch assembly 101, while the second armature assembly 1000 is onan output end of the dual-clutch assembly 101, and so extends a meansfor coupling torque downstream. The first input shaft 600 is omitted inthis Figure, but it extends from spindle 1210, through dual-clutchassembly, and within the second input shaft 650 as a means for couplingtorque downstream.

With reference to FIGS. 3, 9 & 10, first armature assembly comprises adust cover 1240 or 1241 coupled via fastener 1251 to a cushion 1231 andto first armature plate 1221. The cushion 1231 can be one or more of anoise dampening material, a flexible material, or elastomeric material.In FIGS. 1 and 9, the dust cover 1241 is stamped to comprise a shape andcomprises a coupling hole 1261. Pin 630 can extend through coupling hole1261, through coupling hole 1211 in spindle 1210 and in to bore 603 offirst input shaft 600. This secures dust cover 1241 to the firstarmature assembly 1100. Alternatively, dust cover 1240 can besnap-fitted.

A spline coupling can be between end spline 601 of first input shaft 600and inner spline within spindle 1210. A bias assembly 1280 can beincluded within dust cover 1241. Fingers 1213 press on bias assembly1280. When a first electromagnetic signal draws first armature plate1221 towards first clutch rotor 1101, coupling surface 1222 of firstarmature assembly 1200 couples to coupling surface 1105 of first clutchassembly 1100. Torque can transfer along first flow path FFP (FIG. 5C).When the first electromagnetic signal is terminated, a spring force aidsin disconnecting the coupling surfaces 1105, 1222. Thereby, the firstarmature assembly 1200 disconnects torque transfer through the firstclutch assembly 1100. The rotatable hub 850 is disconnected from boththe first input shaft 600 and the from the second input shaft 650.

The spring force can be attained by including a flexure aspect in thecushion 1231 so that when the first armature plate 1221 is fastened tothe cushion 1231, the cushion can be biased to return to a position thatdraws the first armature plate 1221 away from the first clutch rotor1101. Further, cushion 1231 can be fastened to the dust cover 1240 or1241, and the dust cover can be designed to bias the first armatureplate 1221 away from the first clutch rotor 1101. This can be achievedby one or more of shaped stampings illustrated on dust cover 1241 andstrategic placement of fasteners 1251. Designing the dust cover tocomprise a flexure aspect can provide the requisite spring force. A biasassembly 1280 comprising flexing discs can additionally or alternativelyprovide spring force.

A further alternative is for first armature assembly 1200 to comprisedrive straps 1260 and so operate similarly to second armature assembly1000. A coupling surface 1012 on second armature plate 1011 facescoupling surface 922 on second clutch rotor 900. Drive straps 1031connect between the second armature plate 1011 and an armature hub 1010.The armature hub 1010 can comprise a triangular shape (FIG. 3), fingers1021 (FIG. 10), or another shape, such as that of fingers 1213 (FIG. 9).Armature hub 1010 is coupled to or integrally formed with rotatablesecond input shaft 650.

When a second electromagnetic signal is applied, the second armatureplate 1011 is drawn towards second clutch rotor 900 and torque can betransferred along second flow path SFP (FIG. 5B). When the secondelectromagnetic signal is terminated, in order to return the firstarmature assembly and the second armature assembly to a neutralposition, a spring force in drive straps 1031 aids in disconnecting thecoupling surfaces 1012, 922. Thereby, the second armature assembly 1000disconnects torque transfer through the second clutch assembly 9000. Therotatable hub 850 is disconnected from both the rotatable first inputshaft 600 and the from the rotatable second input shaft 650 and torqueis limited to flow through neutral flow path NFP (FIG. 5A) wherebyrotatable hub 850 rotates with the first clutch rotor 1101 and thesecond clutch rotor 900.

The coupling surfaces can comprise respective grooves, such as grooves911, 912, 913 formed in coupling surface 922, and grooves 1107 formed incoupling surface 1105, or grooves 1013 formed in second armature plate1011, etc., for functions such as heat dissipation, wiping, torquetransfer control or the like. In some applications, it is beneficial toprovide a friction material seated in the grooves.

FIG. 4 shows one arrangement of a dual-clutch assembly. The cushion 1231is shown coupled near fingers 1213 to pull first armature plate 1221away from first clutch rotor 1101 to form a first gap G1 there betweenin the neutral condition. A second gap G2 is formed between secondclutch rotor 900 and second armature plate 1011 by drive straps 1031biased between armature hub 1010 and second armature plate 1011.

In FIG. 4, second input shaft 650 is integrally molded with armature hub1010, while first input shaft 600 is omitted. FIG. 6 illustrates oneexample of first input shaft 600, and end spline 601 and bore 603 forpin 630 can be seen. The first input shaft 600 is stepped in response toassembly techniques and the diameters and lengths of the steppedportions are chosen for design purposes, such as bearing or gear sizes,inertia, and stability. For example, the length of bearing surface 605can be chosen based on whether ball bearings like first bearings 110 areused or other bearings such as needle bearings are used to mountrotatable hub 850 with respect to the first input shaft 600. Firstbearings 110 comprise balls 111 between races. First bearings 110 permitrotatable hub 850 to rotate around first input shaft 600 during theneutral condition without also rotating the first input shaft 600. Firstclutch assembly 1100 must be engaged (FIG. 5C) in order for first inputshaft 600 to rotate with rotatable hub 850. A spacer 670 can separateand axially restrict first bearings 110 along bearing surface 605. Whenpin 630 is secured in bore 603, spindle 1210 can axially restrict firstbearings 110 in a first axial direction along axis P-P, and an edge ofintegral spacer 607 can axially restrict first bearings 110 in a secondaxial direction along axis P-P.

A second portion 608 of the first input shaft 600 is surrounded by thesecond input shaft 650. So, a second bearing surface 609 can be formedto support one or both second bearings 130. When second input shaft 650steps down, second portion 608 can also be stepped such that thirdbearing surface 611 is formed complementary to a step down in secondinput shaft 650. Third bearing surface 611 can support a second of thesecond bearings 130 and can also support one of the constant mesh gearsof the transmission assembly 105, such as first gear 7080. A fourthbearing surface 613 can be included for supporting a first end platebearing 140 that permits the first input shaft 600 to rotate relative toand be supported by the end plate 16. First portion 606 of input shaft600 spans through the dual-clutch assembly 101 and second portion 608transitions in to the transmission assembly 105. As above, thedual-clutch assembly can be a dry assembly, while the transmissionassembly 105 can be a wet assembly, and so seal 15 can couple to firstinput shaft 600 and does so in the example on second portion 608 at theend of second bearing surface 609.

Second input shaft 650 is rotatable and surrounds the second portion 608of the rotatable first input shaft 600. Rotatable second input shaft isconcentric with the rotatable first input shaft about the axis P-P.Second input shaft 650 can comprise internal and external steps, whichfacilitates necking-down the transmission assembly 105 for smallpackaging. Internal steps can be bearing surfaces, such as bearingsurface 652, for second bearings 130 so that second input shaft 650 canrotate relative to the first input shaft 600 without rotating the firstinput shaft 600 and vice versa. Another step can be included in internalsurface of second input shaft to accommodate seal 15. External steps canaccommodate seal 13 and can comprise a gear surface 651 for mountingsecond gear 7030. Alternatively, second gear 7030 can be integrallyformed with the second input shaft 650 in the location of gear surface651.

A rotatable hub 850 surrounds the first portion 606 of the rotatablefirst input shaft 600. A limiter rim 851 can be included on therotatable hub 850 to limit vibratory motion of the rotatable hub 850with respect to the spacer 670. First clutch rotor 1101 is connected tothe rotatable hub 850 as by press-fitting an inner surface of the firstclutch rotor 1101 to an outer surface of the rotatable hub 850. Firstclutch rotor 1101 can comprise a cup shape so as to provide a surfacefor pulley coupling 1103, a surface for coupling surface 1105, and asurface for fitting to rotating hub 850. The cup-shape can be configuredto surround a portion of electromagnetic mounting hub 800 associatedwith first coil winding 811.

A second clutch rotor 900 is connected to the rotatable hub 850 as bypress-fitting a bore surface 935 of the second clutch rotor 900 toanother outer surface of the rotatable hub 850. Second clutch rotor 900can also comprise a cup shape and also provide for coupling surface 922.The cup-shape can be configured to surround a second portion ofelectromagnetic hub associated with second coil winding 812. Inner lipsurface 933 and outer lip surface 931 surround a portion of second core802 but do not physically coupled thereto. A like arrangement of innerand outer lips can be included on first clutch rotor 1101 to surround aportion of first core 801.

First clutch rotor 1101 and second clutch rotor 900 are fixed torotatable hub 850 and these can rotate together when torque is appliedto pulley coupling 1103. A bearing 120 is included betweenelectromagnetic mounting hub 800 and rotatable hub 850 so thatelectromagnetic assembly 8000 can remain stationary while the rotatablehub 850 rotates. Among other bearing types, bearing 120 can compriseneedles 121 and constitute a needle bearing.

A control device can be coupled to control plug 810 to supply electricsignals to the first and second coil windings 811, 812 and therebyinduce electromagnetic signals that can attract one of the first andsecond armature plates 1221, 1011 for torque coupling through thedual-clutch assembly.

Electromagnetic assembly 8000 can comprise an electromagnetic mountinghub 800. As in FIG. 4, first and second spools 813, 814 can be includedfor receiving first and second coil windings 811, 812, orelectromagnetic assembly 8000 can be spool-less as shown in FIGS. 5A-5C.First core receptacle 805 can receive first coil winding 811 and secondcore receptacle 806 can receive second coil winding 812. Anencapsulation layer 820 can be applied to secure the first and secondcoil windings 811, 812 in place and to provide shape and requisiteinsulation. The encapsulation layer can leak in to first and second corereceptacles 805, 806 and can be leaked to other areas as needed, such asto channels for wiring or for forming the control plug 810. Innersurface 803 can be spaced from the cup-shaped rotors, but be fitted tothe bearing 120. A second inner surface 804 can be formed by steppingthe electromagnetic mounting hub 800, which can control electromagneticsignal placement with respect to the other components.

The stationary electromagnetic assembly 8000 comprises electromagneticmounting hub 800 mounted between the first clutch rotor 1101 and thesecond clutch rotor 900. The electromagnetic assembly 8000 is configuredto emit at least a first electromagnetic signal and a secondelectromagnetic signal. First armature assembly 1200 is coupled to thefirst input shaft 600. The first armature assembly 1200 is configured tocouple to the first clutch assembly coupling surface 1105 of the firstclutch rotor 1101 when the electromagnetic assembly 8000 emits the firstelectromagnetic signal. A second armature assembly 1000 is coupled tothe second input shaft 650. The second armature assembly 1000 isconfigured to couple to the second clutch coupling surface 922 of thesecond clutch rotor 900 when the electromagnetic assembly 8000 emits thesecond electromagnetic signal. Absent the first electromagnetic signaland the second electromagnetic signal, the rotatable hub rotates 850,but neither the rotatable first input shaft 600 nor the rotatable secondinput shaft 650 rotate.

When the dual-clutch assembly 101 is coupled to the transmissionassembly 105, the concentric first input shaft 600 and second inputshaft 650 are coupled to gears that are in constant mesh with countershaft 700. Counter shaft 700 can comprise an integrally formed gear,such as second output gear 703. One or both of the first output gear 708and the second output gear 703 can be integrally formed with the countershaft 700 to connect to the counter shaft. Alternatively oradditionally, gear surfaces can be included, such as gear surface 705,and a gear such as first output gear 708 can be press-fit to the gearsurface 705. Other surfaces can be formed in counter shaft 700 forassembly or other purposes, such that counter shaft 700 can be steppedor ringed. For example, bearing surfaces 701 & 707 can be included sothat the counter shaft 700 can be mounted with respect to the housing 10and with respect to the end plate 16. A countershaft bearing 150 such asa needle bearing and a second end plate bearing 160 such as a ballbearing can be included so that the counter shaft 700 can rotate withthe housing 10 and end plate 16 remain stationary. A coupler surface 709can be included in the countershaft 700 for receiving the coupler 2010for coupling to an end device, such as a supercharger. Snap rings orbushings can be included where necessary to maintain positions ofbearings and gears along the Q-Q axis.

A gear set for a two speed, dual clutch transmission can comprise arotatable first input shaft 600 and a first gear 7080 comprising a firstgear ratio coupled to the first input shaft 600. A rotatable secondinput shaft 650 can surround a portion 608 of the first input shaft 600.The second input shaft 650 can be concentric with the first input shaft600 about an axis P-P. A second gear 7030 can comprise a second gearratio coupled to the second input shaft 650. A counter shaft 700 can beparallel along an axis Q-Q to the first input shaft 600. The countershaft 700 forms a torque output for the transmission assembly 105. Afirst output gear 708 can be connected to the counter shaft 700, thefirst output gear 708 coupled to transfer torque from the first gear7080. First gear 7080 receives torque from pulley coupling 1103 when thefirst clutch assembly 1100 is electromagnetically clamped to close firstgap G1. Then, first clutch rotor 1101 passes torque to first armatureassembly 1200, which passes torque to the first input shaft 600. Asecond output gear 703 can be connected to the counter shaft 700, thesecond output gear 703 coupled to transfer torque from the second gear7030. The second gear 7030 receives torque from pulley coupling 1103when the second clutch assembly 9000, which is linked via rotatable hub850 to the first pulley coupling 1103 of first clutch rotor 1101, iselectromagnetically clamped to close second gap G2. Then, second clutchrotor 900 passes torque to the second armature assembly 1000, whichpasses torque to second input shaft 650. First gear 7080 is in constantmesh with the first output gear 708. Second gear 7030 is in constantmesh with the second output gear 703. First gear 7080 and first outputgear 708 are configured to rotate the counter shaft 700 at a first driveratio while second gear 7030 and second output gear 703 are configuredto rotate the counter shaft 700 at a second drive ratio.

Other implementations will be apparent to those skilled in the art fromconsideration of the specification and practice of the examplesdisclosed herein.

What is claimed is:
 1. A dual-clutch assembly, comprising: a rotatablefirst input shaft comprising a first portion and a second portion; arotatable second input shaft surrounding the first portion of the firstrotatable input shaft, the second input shaft concentric with the firstinput shaft; a rotatable hub surrounding the second portion of the firstinput shaft; a first clutch rotor connected to the rotatable hub, thefirst clutch rotor comprising a pulley coupling and a first clutchcoupling surface; a second clutch rotor connected to the rotatable hub,the second clutch rotor comprising a second clutch coupling surface; astationary electromagnetic assembly mounted between the first clutchrotor and the second clutch rotor, the electromagnetic assemblyconfigured to emit at least a first electromagnetic signal and a secondelectromagnetic signal; a first armature assembly coupled to the firstinput shaft, the first armature assembly configured to couple to thefirst clutch coupling surface of the first clutch rotor when theelectromagnetic assembly emits the first electromagnetic signal; and asecond armature assembly coupled to the second input shaft, the secondarmature assembly configured to couple to the second clutch couplingsurface of the second clutch rotor when the electromagnetic assemblyemits the second electromagnetic signal.
 2. The dual-clutch assembly ofclaim 1, further comprising a bearing between the electromagneticassembly and the rotatable hub, the bearing configured so that therotatable hub can rotate with the first clutch rotor and with the secondclutch rotor while the electromagnetic assembly remains stationary. 3.The dual-clutch assembly of claim 1, wherein, when a pulley couplestorque to the pulley coupling surface, and absent the firstelectromagnetic signal and the second electromagnetic signal, therotatable hub rotates, but neither the first rotatable input shaft northe second rotatable input shaft rotate.
 4. The dual-clutch assembly ofclaim 1, wherein, when the electromagnetic assembly emits the firstelectromagnetic signal, the first armature assembly couples the firstinput shaft to the first clutch rotor, and the first input shaft isconfigured to under-run a pulley speed of a pulley connected to thepulley coupling.
 5. The dual-clutch assembly of claim 1, wherein, whenthe electromagnetic assembly emits the second electromagnetic signal,the second armature assembly couples the second input shaft to thesecond clutch rotor, and the second input shaft is configured toover-run a pulley speed of a pulley connected to the pulley coupling. 6.A dual-clutch transmission comprising: a dual-clutch assembly,comprising: a rotatable first input shaft comprising a first portion anda second portion; a rotatable second input shaft surrounding the firstportion of the first rotatable input shaft, the second input shaftconcentric with the first input shaft; a rotatable hub surrounding thesecond portion of the first input shaft; a first clutch rotor connectedto the rotatable hub, the first clutch rotor comprising a pulleycoupling and a first clutch coupling surface; a second clutch rotorconnected to the rotatable hub, the second clutch rotor comprising asecond clutch coupling surface; a stationary electromagnetic assemblymounted between the first clutch rotor and the second clutch rotor, theelectromagnetic assembly configured to emit at least a firstelectromagnetic signal and a second electromagnetic signal; a firstarmature assembly coupled to the first input shaft, the first armatureassembly configured to couple to the first clutch coupling surface ofthe first clutch rotor when the electromagnetic assembly emits the firstelectromagnetic signal; and a second armature assembly coupled to thesecond input shaft, the second armature assembly configured to couple tothe second clutch coupling surface of the second clutch rotor when theelectromagnetic assembly emits the second electromagnetic signal; afirst gear coupled to the first input shaft; a second gear coupled tothe second input shaft; a counter shaft forming a torque output; a firstoutput gear connected to the counter shaft, the first output gearcoupled to transfer torque from the first gear; and a second output gearconnected to the counter shaft, the second output gear coupled totransfer torque from the second gear.
 7. The dual-clutch transmission ofclaim 6, wherein the first gear is in constant mesh with the firstoutput gear during operation of the clutch transmission, and wherein thesecond output gear is in constant mesh with the second gear duringoperation of the clutch transmission.
 8. The dual-clutch transmission ofclaim 6, wherein one or both of the first output gear and the secondoutput gear are integrally formed with the counter shaft to connect tothe counter shaft.
 9. The dual-clutch transmission of claim 6, whereinthe first gear and the first output gear are configured to rotate thecounter shaft at a first drive ratio, and wherein the second gear andthe second output gear are configured to rotate the counter shaft at asecond drive ratio.
 10. The dual-clutch transmission of claim 6, furthercomprising: a clutch housing portion surrounding at least the secondarmature assembly and providing a dry environment for the secondarmature assembly; and a gear housing portion surrounding a portion ofthe second rotatable input shaft and providing a fluid-tight containerfor the portion of the second rotatable input shaft.
 11. The dual-clutchtransmission of claim 6, further comprising a coupler for coupling thecounter shaft to a supercharger assembly.
 12. A supercharger assemblycomprising: a dual-clutch assembly, comprising: a rotatable first inputshaft comprising a first portion and a second portion; a rotatablesecond input shaft surrounding the first portion of the first rotatableinput shaft, the second input shaft concentric with the first inputshaft; a rotatable hub surrounding the second portion of the first inputshaft; a first clutch rotor connected to the rotatable hub, the firstclutch rotor comprising a pulley coupling and a first clutch couplingsurface; a second clutch rotor connected to the rotatable hub, thesecond clutch rotor comprising a second clutch coupling surface; astationary electromagnetic assembly mounted between the first clutchrotor and the second clutch rotor, the electromagnetic assemblyconfigured to emit at least a first electromagnetic signal and a secondelectromagnetic signal; a first armature assembly coupled to the firstinput shaft, the first armature assembly configured to couple to thefirst clutch coupling surface of the first clutch rotor when theelectromagnetic assembly emits the first electromagnetic signal; and asecond armature assembly coupled to the second input shaft, the secondarmature assembly configured to couple to the second clutch couplingsurface of the second clutch rotor when the electromagnetic assemblyemits the second electromagnetic signal; a supercharger input shaftmechanically coupled to the clutch transmission, the superchargerassembly configured to selectively convert between a neutral operationmode, a first drive ratio operation mode, and a second drive ratiooperation mode in response to the presence or absence of the firstelectromagnetic signal and the second electromagnetic signal.
 13. Thesupercharger assembly of claim 12, comprising a pair of lobed rotors,wherein the pair of lobed rotors are mechanically coupled to thesupercharger input shaft, and wherein the neutral operation mode doesnot transfer torque from the clutch transmission to the pair of lobedrotors.
 14. The supercharger assembly of claim 12, further comprising atransmission assembly, comprising: a rotatable first input shaft; afirst gear comprising a first gear ratio coupled to the first inputshaft; a rotatable second input shaft surrounding a portion of the firstinput shaft, the second input shaft concentric with the first inputshaft; a second gear comprising a second gear ratio coupled to thesecond input shaft; a counter shaft parallel to the first input shaft; afirst output gear connected to the counter shaft, the first output gearcoupled to transfer torque from the first gear; and a second output gearconnected to the counter shaft, the second output gear coupled totransfer torque from the second gear, wherein the first gear is inconstant mesh with the first output gear, and wherein the second outputgear is in constant mesh with the second gear.
 15. The superchargerassembly of claim 14, wherein the first gear and the first output gearare configured to rotate the counter shaft at a first drive ratio, andwherein the second gear and the second output gear are configured torotate the counter shaft at a second drive ratio.